1. Field of the Invention
This invention relates to a wound golf ball having a solid center, which is improved in flight performance, spin, and durability.
2. Prior Art
Prior art wound golf balls of the solid center type include those having ionomer resin covers and those having balata rubber covers. As compared with the wound balata balls, the wound golf balls using ionomer resins as the cover stock are superior in flight distance on driver shots, but inferior in spin properties necessary for approach play on the green (an appropriate stop on the green). On the other hand, the wound balata balls are less durable, for example, in that their cover presenting the ball surface can be scuffed or fretted by bunker shots and cut when topped with iron clubs.
To solve the above-mentioned problems, the assignee of the present invention proposed several wound golf balls having a solid center and a cover of multilayer structure including outer and inner layers, for example, in U.S. Pat. No. 5,628,699 a wound golf ball wherein the cover outer layer has a gage of at least 0.4 mm; in U.S. Ser. No. 08/659259, a wound golf ball wherein the cover inner layer is formed of an ionomer resin having an acid content of less than 15% by weight and the cover outer layer is formed of a resin having a Shore D hardness of 43 to 53; in U.S. Ser. No. 09/41017, a wound golf ball wherein an adhesive layer is interleaved between the cover inner and outer layers; and a wound golf ball wherein the solid center has an outer diameter of 27 to 38 mm and a distortion of 1.5 to 3.5 mm under a load of 30 kg, the ball shows a rebound height of at least 96 cm when dropped from a height of 120 cm, and has a total number of 350 to 500 dimples and a dimple volume/ball volume proportion of 0.76 to 0.9%. These balls are improved in that they travel a distance at least equal to the prior art wound golf balls having a solid center enclosed with a high hardness ionomer resin cover, they exhibit spin properties comparable to the wound balata balls, and their cover is not readily cut when topped with iron clubs.
There is still a desire to have a wound golf ball which is more superior in flight distance, spin and durability.
There was also proposed in JP-B 44303/1993 a golf ball in which the cover is formed to a high degree of whiteness from a cover stock comprising 100 parts of an ionomer resin and 1 to 10 parts by weight of an inorganic white pigment containing at least 50% by weight of barium sulfate having a particle size of 1 to 10 .mu.m.
JP-B 48473/1992 disclose a solid golf ball having a cover of two-layer structure of outer and inner layers in which the specific gravity, gage and Shore D hardness of the cover layers are restricted to specific ranges, and the cover inner layer is adjusted using a filler (e.g., tungsten or molybdenum) having a specific gravity of 10 to 20. Since the cover of this golf ball is formed by compression molding, it is difficult to achieve full amalgamation of the cover stock to the thread rubber layer and hence, the cover becomes less durable. Another drawback is that the ball is less satisfactory in spin when hit with a short iron.